1. Field of the Invention
There is a need for novel markers which are particularly suitable for marking water immiscible organic liquids such as petroleum fuels and which markers may be extracted easily from said marked liquids and identified. There is also a need for marked fuels and for means to mark, tag or otherwise identify petroleum fuels or other organic solvents, and to distinguish such marked liquids from the otherwise identical but unmarked substances.
These needs arise primarily from differing price or tax structures of different fuels or even the same fuel used for different purposes. For example, gasoline used for off-highway, non-vehicular purposes such as mining, lumbering or fishing, is commonly taxed at lower rates than that for highway vehicular use. Further, certain grades of oil are used interchangeably for heating oil or for diesel motor fuel. These situations can lead to abuse of the tax laws and cheating by unscrupulous persons.
It is, of course, necessary that the added chemical marker be capable of quick and relatively simple identification by non-scientific personnel. In other instances and aside from tax matters, there are occasions when it is desirable to mark a particular production batch of fuel or solvent to prove the origin of the material. As is readily apparent, any marker so used must be added in small concentration, should not affect the physical or chemical properties of the substances to which it is added and should be easily identified by relatively quick and simple means.
It is desirable to have simple, rapid and sensitive methods to detect the presence of one petroleum product in another. Fuels are sometimes mixed for the purpose of adulterating a higher priced product with a lower priced material, such as the addition of regular grade gasoline to premium gasoline, or for the purpose of evading taxation by the addition of low-taxed light heating oil to highly taxed diesel fuel. Other reasons for identifying particular fuels are determination of theft, or locating leaks from storage facilities at service stations, oil terminals, large scale industrial lubrication systems, or automotive transmission and hydraulic systems.
2. Description of the Prior Art
Among the many additives and tracers which have been proposed for use or are in current use for marking or tagging motive fuels and other petroleum distillates are the metal-organic compounds, radioactive substances, and a variety of specific compounds which react with selected agents to provide intensely colored derivatives. However, many of the proposed additives and those in use have certain disadvantages which render them impractical for marking purposes. For example, the metal-organic compounds have relatively poor storage stability. The use of radioactive substances requires special equipment and precautionary measures to prevent harmful physiological disturbances to personnel. With respect to the specific compounds which have been employed for marking purposes, there may be mentioned quinizarin, furfural, diphenylamine, and various naphthol derivatives.
Quinizarin, though an excellent marker which is extracted from petroleum fuels by aqueous caustic solutions, suffers from the disadvantage of low solvent solubility, i.e., its solubility is generally of the order of magnitude of about 1 percent or less in the commonly used solvents. The relative insolubility of quinizarin in fuel-compatible solvents means that it must be transported and used in dry state with the attendant handling problems due to dusting and low solubility, and precludes the possibility of providing a solution containing as much as about 20 or 40% quinizarin. The use of a relatively dilute quinizarin solution would require the handling, storage and metering of large volumes, a situation which is undesirable both from a handling and economic point of view.
Furfural develops an intense red-colored complex with aniline acetate. However, the furfural test is extremely sensitive and the smallest contamination by any furfural naturally present in the liquid to be marked yields a distinct red color. Since a small quantity of furfural is sometimes produced in the normal production of middle petroleum distillates, a positive furfural test is not necessarily conclusive evidence of the presence of added furfural. The same is true of diphenyl amine and various naphthols which may originate in crude oil or arise from the cracking or refining process. Further, at the concentrations generally used in fuels, furfural is unstable to the extent that no positive identification will be obtained after a normal storage period of up to six months. Other specific marking agents, for example, aniline azo beta naphthol, are extracted from fuels to which they are added by the extractants dimethylformamide or benzyl alcohol to yield a yellow colored extract. However, some times a yellow extract can be obtained from unmarked petroleum fuels, thereby vitiating the test. Oil soluble dyes such as Solvent Red #24 and Solvent Red # 19 have also been used for marking fuels, with identification dependent upon dye recognition.
Accordingly, it would be desirable and is an object of this invention to provide novel markers for petroleum fuels, which markers have the following characteristics:
1. Entirely foreign to the fuel.
2. Can be supplied as liquids having high solubilities in petroleum fuels.
3. Colorless.
4. Do not alter the appearance of the fuel to which added.
5. Easily extracted from the marked fuel.
6. When extracted from the marked fuel, they are easily identified by a simple, on-the-spot test which is not subject to interference by the components of the fuel.
7. The identification can be corroborated by laboratory methods, if necessary.
The fulfillment of these desiderata and objects of this invention may be more readily appreciated by reference to the following specification, examples and appended claims.